Victory for the Europa League finalists would have seen them move above Lyon and Monaco into second position in the table, but they stay down in fourth following an eventful 90 minutes at the Stade de Roudourou.
The visitors might have doubled their lead in the 11th minute when Germain turned provider to feed Morgan Sanson, but the midfielder saw his effort blocked.
Sanson almost put the match beyond Guingamp in the 39th minute when he sent a header towards the bottom corner, but Johnsson was on hand to make a smart save, and the hosts had one back just three minutes later.
The goal came from Clement Grenier, with the 27-year-old finding space inside the Marseille box before finishing past Mandanda to leave the match delicately poised ahead of the second period.
Guingamp did not need long to level the scores, with Grenier converting from the penalty spot in the 52nd minute after Ocampos had been penalised for a handball inside the box.
It went from bad to worse for Marseille in the 69th minute when they conceded their second penalty of the match in an incident that saw their goalkeeper Mandanda receive a straight red card.
Marseille were back on terms in the 81st minute, however, when Thauvin converted a low Bouna Sarr cross to set up a potential grandstand finish.
Both teams had half-chances in the final 10 minutes of action, but the points were ultimately shared on the night.
GUINGAMP (4-5-1): Johnsson; Ikoko, Sorbon, Kerbrat, Eboa Eboa; Thuram, Deaux (Salibur 88'), Grenier, Didot (Diallo 88'), Benezet (Coco 79'); Briand
MARSEILLE (4-5-1): Mandanda; Sakai, Sertic, Kamara, Amavi; Thauvin, Lopez (N'Jie 64'), Zambo, Sanson, Ocampos (Sarr 73'); Germain (Pele 69')body check tags ::